Cases of yellow fever have been on the rise in various parts of South America, tripling 2024 numbers for the mosquito-borne disease and resulting in a startling uptick in human deaths.
As the University of Minnesota's Center for Infectious Disease Research and Policy shared in mid-May, five South American countries confirmed 212 cases of yellow fever and 85 deaths related to the disease.
These numbers reflect cases from late December 2024 to April 26, 2025. Most were in Brazil, followed by Colombia, Peru, Ecuador, and Bolivia.
Although the 2024 cases of yellow fever centered on the Amazon region, 2025 cases have been predominantly found further from the river. This trend may indicate that mosquitoes carrying yellow fever are spreading to new areas to impact larger population centers.
Mosquito-borne diseases, including yellow fever and dengue fever, are increasing threats as our planet continues to warm due to human-caused pollution. Higher temperatures and damp conditions exacerbated by rising global temperatures create ideal breeding grounds for mosquitoes.
Various infectious disease risks are trending up worldwide as a result of environmental conditions, and many experts agree that governments aren't sufficiently prepared to deal with the public health implications. In addition to these five South American countries, mosquito-borne diseases are a growing concern in the United States and many other places.
With pollution levels contributing to extreme heat and weather events, enabling mosquitoes to travel to territories once inhospitable to them, researchers worry that human cases and deaths could rise in the years ahead.
To inform the public, the World Health Organization released a disease outbreak update detailing the yellow fever situation in South America. It described how the governments of Bolivia, Brazil, Colombia, Peru, and Ecuador have responded to the yellow fever outbreaks by increasing preventive measures, including testing, monitoring, and immunization efforts.
"WHO emphasizes the importance of active surveillance … Vaccination remains the primary means for preventing and controlling yellow fever," the WHO said.
With vaccination, yellow fever is a preventable disease. The WHO recommends immunizations for individuals over nine months old.
Getting vaccinated against yellow fever is important, especially for those living in or planning to travel to a region impacted by an outbreak. Individuals can also attempt to prevent the mosquito bites that can lead to infection by using insect repellent, wearing protective clothing, and avoiding being outdoors during times of high mosquito activity.
The WHO additionally underscored the need for critical activities like cross-border coordination and information sharing to prevent further disease outbreaks. As climate researchers, policymakers, and community advocates also work to mitigate infections by making breeding grounds less appealing to warm- and wet-loving mosquitoes, sharing knowledge about critical climate issues can play a role in human health, especially in marginalized populations.
All five of the nations listed in the WHO yellow fever update are low- and middle-income countries, which disproportionately experience the effects of a warming climate.
危險疾病在多個國家爆發，衛生官員宣布緊急狀態：“強調主動監測的重要性”
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